Silencer or muffler



1366- 1953 F. a. DEREMER SILENCER OR MUFFLER 2 Sheets-Sheet 1 Filed Aug. 9, 1950 3nnentor2 1101 2 E. .UEHEMEJZ.

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(Itto neg Dec. 1, 1953 Filed Aug. 9, 1950 F. E. DEREMER 2,661,073

SILENGER OR MUFFLER 2 Sheets-Sheet 2 Ihwcnfor 2 TL DYE I .EEJZEMER Patented Dec. 1, 1953 UNITED STATES PATENT OFFICE SILENCER OR MUFFLER Application August 9, 1950, Serial No. 178,430

8 Claims.

This invention relates to sound attenuating devices and more especially tosilencers or mufflers for use with exhaust systems of internal combustion engines of automotive vehicles.

Many different types of silencing devices have been devised and used with the exhaust systems of internal combustion engines or moving gas streams in an endeavor to eliminate or attenuate the sound Waves entrained in the gas stream to the greatest possible extent. The interior construction of a sound attenuating muliler is usually provided With gas passages, resonating or sound attenuating chambers and other sound trap arrangements for the purpose of attenuating sound waves with the least possible back pressure to the gas stream. While theuse of perforations for connecting a gas stream and sound wave passage with one or more sound trap chambers is elfective to attenuate sound waves, the muffler shell forming the outer Wall of the sound trap or resonance chambers is subjected to vibrations under the influence of impinging sound waves. Such vibratory action of the mufller shell is usually referred to as shell noise.

The elimination of shell noise is a problem which has confronted manufacturers of sound attenuating devices for the reason that shell vibration characteristics resulting in shell noises vary with the types and sizes of muffler construction and the character of the exhaust gas stream and the Wave lengths of sound waves entrained therein.

In certain types of muiller construction a double shell has been utilized and the space between the shells packed with asbestos or other similar resilient fireproof packing material for the purpose of reducing or damping the vibration of the shell. In my prior Patent No. 2,151,084, granted March 21, 1939, I disclosed a mufiier wherein the inner shell is formed with pressed-out spots or dimples engageable with an outer shell for reducing shell noise. I found that the construction of my prior patent, while effective in some installations, does not in all installations satisfactorily eliminate shell noise.

The present invention embraces the provision of a silencer or mufiler construction embodying a multiply or double wall shell formed so as to provide a plurality of spaced chambers for effectively minimizing or eliminating shell noise.

An object of the invention is the provision of a silencer or mulfier construction embodying a double wall shell in which at least one wall is configurated to form with the other wall a plurality of isolated or spaced air chambers for efiectively reducing the vibration of the shell construction set up by impinging sound waves of the gas stream moving through the silencer.

Another object of the invention includes the formation of a multiply wall construction for a tubular sound attenuating instrumentality wherein one of the wall plies is provided with spaced linear ridges engageable with another wall ply whereby the vibration of the wall construction under the influence of sound waves impinging thereon is reduced and shell noise therefore substantially reduced.

Still another object of the invention is the provision of a silencer or muflier for a moving gas stream wherein the silencer shell construction embodies double walls one of which is formed with spaced parallel ridges or raised portions engageable with the other Wall in a manner to form spaced chambers and reinforcement or cushioning means for the inner wall whereby the normal periodicity of vibration of the shell wall construction is altered and audible sounds or shell noise illustrating a modified form of mufiier shell conset up by impinging sound waves is substantially reduced.

Still a further object is the provision of a muilier shell construction embodying a double wall arrangement providing a plurality of spaced air chambers whereby shell noise is eliminated or greatly reduced Without the use of asbestos filler or other packing material thus substantially reducing the cost of producing a double wall mufiler which will be commercially acceptable.

Further objects and advantages are within the scope of this invention such as relate to the arrangement, operation and function of the related elements of the structure, to various details of construction and to combinations of parts, elements per se, and to economics of manufacture and numerous other features as will be apparent from a consideration of the specification and drawing of a form of the invention, which may be preferred, in which:

Figure 1 is a longitudinal sectional view of a muffler construction embodying my invention;

Figure 2 is a transverse sectional view through the muffler taken substantially on the line 2-2 of Figure 1;

Figure 3 is an enlarged fragmentary isometric view illustrating a form of dual wall shell construction of the muflier illustrated in Figure 1;

Figure 4 is a sectional view similar to Figure 2 struction of my invention;

Figure 5 is a fragmentary isometric view illustrating in detail the shell construction shown in v Figure 4 Figure 6 is a transverse sectional view illustrating a form of my invention as embodied in a circular or cylindrical type muffler;

Figure 7 is an enlarged fragmentary isometric view illustrating in detail the shell construction of Figure 6;

Figure 8 is an elevational view partly in section illustrating a muffler of the general type shown in Figure 1 with corrugations in one oi the shell walls disposed in circumferential parallelism;

Figure 9 is a fragmentary detail sectional view taken substantially on the line 99 of Figure 8;

Figure 10 is a sectional view illustrating a modified form of the muffler construction shown in Figure 8, and

Figure 11 is a sectional view illustrating a multiply muffler shell formed of a single sheet of metal rolled upon itself.

While I have illustrated the shell construction of my invention as embodied in a type of muffler or silencer incorporating offset gas passage tubes and embodying certain forms of sound attenuating or resonance chambers and devices, it is to be understood that the shell construction may be utilized with any type of silencer or muffler for attenuating sound waves of a moving gas stream.

With particular reference to the form of my invention as illustrated in Figures 1 to 3, the muffler or silencer I is formed with a multiply or dual wall shell comprising an inner shell memher or wall I l and an outer shell member or wall l2. The shell members If and I2 are formed to generally elliptical or oval configuration as shown in Figure 2 but it is to be understood that the exterior muffler contour may be of any desired shape or configuration. The members if and ii. in this form of the invention constituting the dual wall shell are independent sheets of metal coextensively assembled and joined together by an overlapping seam l3. If desired they may be welded together in lieu of the joining seam.

The muffler shell construction is provided at each end with heads I4 and I having peripheral flange portions l! which embrace the ends of the shell construction to form closures for the muffler. It is to be understood that any suitable arrangement may be employed for securing the end heads in position. In Figure 1 the flange ll on each head embraces the multiply shell construction and is rolled to form an inwardly extending bead H! which engages in a circumferential groove in the member I l to secure the head to the shell.

As particularly shown in Figure 2 the inner ply or wall II is of smooth contour While the outer ply or wall I2 is formed with spaced longitudinally disposed, inwardly-extending ridges [9 or flutes forming spaced portions 28 providing longitudinally arranged air chambers 21 formed between pairs of ridges l9, inner wall I l and raised portions 20. As the outer and inner shell members II and l2 are joined to the heads 14 and IS in a manner to terminate the chambers 2| adjacent the heads, it will be apparent that the chambers 2| are individual in nature and isolated from each other so that there is no circulation of air through the chambers. The ridges IQ engaging the inner wall at spaced zones reinforce the inner wall and modifies its normal periodicity of vibration. The chambers 2i form dead air spaces or air cushions which in cooperation with the reinforcing ridges 19 function to damp vibrations of the inner and outer shells H and I2 and hence greatly reduce or minimize shell noise in the mufller.

The mufiier is formed with a gas inlet passage through an opening in the end head l4 and which is Welded or otherwise secured to a flange 23 surrounding the opening in the head to receive the entrance tube 22. The tube 22 is telescopingly connected with a second tube 24 which conveys the gases to a midportion of the muffler. The muffler is provided adjacent its central portion with a pair of longitudinally spaced walls or partitions 25 and 25 to provide what may be termed a gas expansion and sound attenuating chamber 21. The interior of the muffler is also provided with sets of partitions 29 and 30. These partitions together with the walls 25 and 26 form resonance or sound attenuating chambers 3| and 32 and gas passage transfer chambers 33 and 34. Each of the partitions 29 and 30 are provided with openings or acoustic couplings 33 and 34', which establish communication with the resonance chambers 3| and 32, the latter serving to attenuate sound waves entering the mufller entrained in the gas stream.

The muffler construction is provided with a gas outlet passage 35 which includes an exit tube 35 secured to an opening in the head or header [5 in the same manner that entrance tube 22' is secured in header [4. The gas exit tube or passage includes a duct or tubular member 38 telescopingly connected with the exit tube 35 as shown in Figure 1. Both the gas inlet tube 24 and the gas exit tube 38 extend through openings formed in the walls or partitions 25 and 2G. The portions of these tubes disposed between the walls are provided with series of perforations in the walls thereof to provide for the expansion of gases into chamber 21 and also to form acoustic couplings with the chamber 21 so that the latter serves as a sound trap for attenuating sound waves entering the muffler. The inlet tube 24 is provided with sets of openings designated 39 and outlet tube 38 with similar sets of openings 40.

Disposed between the tubes 24 and 38 in the chamber 21 is a tube 42 surrounded by a second tube 43 of larger diameter, said tubes being respectively provided With a large number of openings in the walls thereof designated 42' and 43' for facilitating cross flow or transverse flow of gases through the chamber 21 as well as to form acoustic couplings for the attenuation of sound waves. The tube 42 is mounted in openings formed in the walls 25 and 26 and is held in place by flanges 45 integrally formed on the walls. The outer tube 43 is held in concentric position with the tube 42 by means of a circular shoulder or ledge 48 formed on each of the walls 25 and 26. The annular space between tubes 42 and 43 is partitioned into two chambers by means of an annular bushing 50 as illustrated in Figure l, the chambers forming sound trap or sound attenuating chambers.

Th functioning of the muffler is as follows: The stream of exhaust gases from an internal combustion engine or other moving gas stream with which the muffler may be used enters the muffler through the gas inlet passage 22 and is conveyed to the gas transfer passage 33. The major amount of gas flows laterally through transfer passage 33 and forwardly through the tube 42 into the gas transfer passage 3 where the gas passes into the outlet duct or tube 38 and is discharged into the atmosphere through a tail pipe 50, some of the gas however passing through the small openings 39 in tube 24 into chamber 2'1". The attenuation of sound waves entrained in or set up by the moving exhaust gas stream is of 22 which includes an entrance tube 22 passing 15 fected through the arrangement of chambers and acoustic couplings or openings. Sound waves of' certain wave lengths are attenuated through the openings 39 in the gas inlet passage tube 24 and others attenuated through the acoustic couplings or openings 42 in tube 42 and openings ii! in tube 43 as well as openings 40 in the gas outlet passage tube 38. In addition to the chamber 21 and the openings from the various tubes forming sound wave attenuating or acoustic damping means they also function to facilitate movement of gases from the inlet tube 24 to the outlet tube 38 through the chamber 21. Thus the chamber 2"! through its acoustic couplings with the inlet and outlet tubes and the tubes 42 and 43 attenuates a large number of the sound waves entrained in the gas stream. Sound waves of oertain lengths are not attenuated in the chamber 21 and hence the sets of resonance or resonator chambers 3| and 32 are provided for attenuating sound waves which are not attenuated through the means of the chamber 2! and the acoustic couplings in the walls of the tubes.

A shell construction of a muffler is subject to vibration because of the energy of the sound waves entering the muffler and impinging on the shell. Vibrations of the shell are set up and these vibrations are usually referred to as shell noise. Many attempts and arrangements have been made to eliminate shell noise. The instant invention provides for a double wall or multiply shell construction arranged so as to form between the shell plies or walls a p1urality of chambers 2| forming dead air spaces or air cushions. In the embodiment of the invention illustrated in Figure 1 none of the exhaust gas entering the mufiler traverses the spaces between the shell walls as they are sealed at the end heads to prevent entrance of exhaust gas into these passages. It is believed that a combination of factors in the construction disclosed is responsible for minimizing or elimination of shell noise in the present invention. The ridges 19 formed in the outer shell engage the inner shell II at the spaced longitudinally extending lines and form a reinforcement which minimizes or reduces the tendency of the inner shell to vibrate. This is enhanced through the provision of the separated dead air spaces 2| which form air cushions to aid in damping vibrations of the inner shell. Moreover, the partitions or walls 25, 26, 29 and 38 are formed with peripheral flanges 55 which may be spot welded to both the inner and outer shells through the ridges I 9 so that the inner and outer shells and the transverse partition walls in the mufiler are secured together at spaced points of welding so as to secure the elements in proper relation. Such Welding also secures the inner and outer shells II and I2 together at spaced points so as to reduce any possibility of relative vibration of any magnitude of one shell wall with respect to the other. Furthermore, such welding or the integration of the shells together through suitable securing means at spaced points aids in eliminating a definite periodicity of vibration of the shell constructon that is inherent in a single wall shell.

A modified form of the invention is illustrated in Figures 4 and 5. In this form of the invention the inner shell 56 is formed with outwardly projecting longitudinally extending ridges 57 which are spaced apart by intermediate portions 58. The outer shell 53 is of smooth contour or shape and is engaged by the ridges 57 to form with the shell a plurality of longitudinally extending air spaces 60 which correspond in function to the air spaces 2'! in the form of the invention mus trated in Figures 1 through 3 inclusive. If desired, the ridges 5'! may be spot welded at spaced points to the outer shell 59.

Figure 6 is a transverse sectional view illustrating the invention as embodied in a cylindrical muffler in which the shell construction is substantially a cylinder. In this arrangement the inner shell 6! is of smooth cylindrical contour while the outer shell 62 is formed with raised portions 63 and inwardly extending ridges 64 adapted for contact or engagement with the inner shell 6| to form air chambers or spaces 65. The inner chambers 65 in this form of mufiler serve the same purpose as the air chambers 2! in the form of the invention illustrated in Figure 1. The interior construction of the mufiler includes a gas inlet tub 66 and an outlet tube 6'! and resonating chambers (not shown) of the general character illustrated in Figure Figure '7 illustrates a modified form of con-- struction wherein the inner shell ill is of smooth, contour and the exterior shell "H is formed with; longitudinally-extending spaced raised portions. 12 forming channels or space 73 providing dead-1 air chambers extending longitudinally of the mufller construction. The ridges 12 are spaced laterally or circumferentially by portions 14 lying in coextensive engagement with the inner shell I0 and may be spot welded or otherwise secured to the inner shell, if desired. In this form of construction the ridges 72 provide a longitudinal reinforcement for the shell construction to lend rigidity to the arrangement and serve toreduce the shell noise not only by the reinforcement afforded by the ridge construction but the air spaces 73 providing damping cushions formed between the shell walls by such construction.

Figure 8 illustrates a form of muliier construction similar to that shown in Figure 1 but in which the outer shell is formed with cricumferentially-arranged longitudinally-spaced ridges or beads 78 which engage the outer surface of the inner shell 19 to form circumferential air spaces 80. The air spaces in the construction shown in Figure 8 perform substantially the same function as those in the Figure 1 construction.

The interior construction of the mufi'ler shown in Figure 8 is similar to that illustrated in Figure 1 and hence will not be described in further detail.

Figure 10 illustrates a modified form of multiply shell construction of the character shown in the muiiler of Figure 8. In Figure 10 the inner shell is formed with outwardly extending ridges 86 which engage the smooth outer shell 81 forming circumferentially disposed individual air spaces 89 serving substantially the same function as the air spaces 30 in the muffler construction shown in Figure 8. The ridges 36 are preferably spot welded or otherwise secured at spaced points to the outer shell 81.

Figure 11 illustrates a further form of multiply shell construction wherein the double wall is formed of a single sheet of metal such as sheet steel or the like. In this form the sheet may be first formed with spaced ridges 9| in approximately one half of the sheet. The sheet may then be rolled upon itself to oval or circular configuration whereby one ply or wall is formed by the smooth portion of the sheet and the second ply or wall formed by the ridged portion. When so assembled the ridges 9| form air spaces 92 with the smooth wall of the shell construction. As illustrated in Figure 11, the inner ply is smooth 7 and the outer ply formed with ridges or flutes, but it is to be understood that the inner ply may be ridged or fluted and the outer wall smooth, if desired. Either arrangement functions to reduce shell noise in substantially the same man her as in the construction illustrated in Figure 1.

It will be apparent that the forms of the in vention herein disclosed provide a multiply or multiple wall shell for a muiller in which is incorporated a structural arrangement providing for spaced air chambers or ducts which. have been found to greatly minimize or substantially eliminate shell noise, a result which is accomplished without the interposition of packing material: such as asbestos or other fibrous heat resisting material which has been used between spaced shells or mufflers in prior art constructions. Hence, I have produced a muffler in which comparatively thin gauge sheet metal may be used" for the plys or shell wall elements so that an inexpensive and comparatively light weight construction is attained, which may be economically produced in mass quantities.

It is apparent that, within the scope of the invention, modifications and different arrangements may be made other than is herein disclosed, and the present disclosure is illustrative merely, the invention comprehending all variations thereof.

I claim:

1. A muiiler for use with the exhaust system of an internal combustion engine, comprising a tubular inner shell, a tubular oute shell, and front and rear closure heads, said on shell surrounding said inner shell and being or approximately the same length as said inner shell, gas inlet and outlet passages formed in said heads respectively, tubular gas passage means disposed in said i aer shell, said gas passage means having opening the walls thereof forming acoustic couplings with the interior of the inner shell, said outer and inner shells being imperforate, one of said shells being formed with a plurality of substantially parallel ridges which engage with the other shell to provide within the space between said inner and outer shells a plurality of sound attenuating passages, the space between the shells being isolated from the interior of said inner shell whereby sounds entrained in the exhaust gas stream impinging upon said inner shell are damped.

2. A mufiler for use with the exhaust system of an internal combustion engine, comprising a tubular inner shell, a tubular outer shell, and front: and rear closure heads, said outer shell. surrounding said inner shell and being of approximately the same length as said inner shell, gas inlet and outlet passages formed in said heads respectively, tubular gas passage means disposed in said inner shell, said gas passage means having openings in the walls thereof forming acoustic couplings with the interior of the inner shell, said outer and inner shells being imperforate, one of said shells being formed with: a plurality of circumferentially-spaced, parallel, longitudinally-extending ridges which engage with the other shell to form between said shells a plurality of separate, longitudinally extending air chambers which are closed at their ends and which are isolated from one another and from the interior of the inner shell, whereby sounds entrained in the exhaust gas stream and impinging upon said inner shell are damped.

3. A mufiler for use with the exhaust system of an internal combustion engine, comprising a tubular inner shell, a tubular outer shell, and front and rear closure heads, said outer'shell surround ing said inner shell and being of approximately the same length as said inner shell, gas inlet and outlet passages formed in said heads respectively, tubular gas passage means disposed in said inner shell, said gas passage means having openings in the walls thereof forming acoustic couplings with the interior of the inner shell, said outer and inner shells being imperforate, one of said shells being formed with a plurality of circumferentially spaced longitudinally extending channel-shaped ridges, and the portions of said one shell between said ridges being in engage-- ment with the other shell, said channel-shapedridges forming with said other shell a plurality of separate, linearly-extending air chambers which are closed at their ends and which are iso-- lated from the interior of said inner shell, whereby sounds entrained in the exhaust gas stream and impinging upon said inner shell are damped.

4. A muffler for use with the exhaust system of an internal combustion engine, comprising a tubular sheet metal inner shell, a tubular sheet metal outer shell, and front and rear closure heads, said outer shell surrounding said inner shell and being of approximately the same length as said inner shell, said shells at their end zones being in contiguous relation, said closure heads having flange portions embracing the end zones of the shells for securing the shells in fixed relation, gas inlet and outlet passages formed in said heads respectively, tubular gas passage means disposed in said inner shell, said gas passage means having openings in the walls thereof forming acoustic couplings with the interior of the inner shell, said outer and inner shells being imperforate, one of said shells being formed with a plurality of substantially parallel spaced ridges which engage with the other shell to provide within the space between said inner and outer shells a plurality of sound-attenuating passages, said ridges forming reinforcing means for the other shell to reduce vibratory movements thereof, the space between the shells being isolated from the interior of said inner shell whereby sounds entrained in the exhaust gas stream impinging upon sa-id inner shell are damped.

5. A mufller for use with the exhaust system of an internal combustion engine, comprising a r tubular sheet metal inner shell, a tubular sheetmetal outer shell, and front and rear closure heads, said outer shell surrounding said inner shell and being of approximately the same length as said inner shell, said shell walls at their end zones being in contiguous relation, gas inlet and outlet passages formed in said heads respectively, tubular gas passage means disposed in said inner shell, gas passage means having openings in the walls thereof forming acoustic couplings with the interior of the inner shell, said outer and inner shells being imperforate, one of said shells being formed with a plurality of substantially parallel spaced ridges which engage with the other shell, said inner and outer shells being formed from a single sheet of metal rolled upon. itself to tubular configuration, an area of said sheet being provided with said ridges, said ridged area being disposed coextensively with a smooth:

area oi said sheet, whereby spaced portions of the ridged area engage the smootharea to form spaced lineraly arranged sound attenuating chambers between said inner and outer shells, saidchambers being isolated from the interior of said inner shell whereby sounds entrained in the 9 exhaust gas stream impinging upon said inner shell are damped.

6. A muffler for use with the exhaust system of an internal combustion engine, comprising a tubular sheet metal inner shell, a tubular sheet metal outer shell, and front and rear closure heads, said outer shell surrounding said inner shell and being of approximately the same length as said inner shell, said shell walls at their end zones being in contiguous relation, gas inlet and outlet passages formed in said heads respectively, tubular gas passage means disposed in said inner shell, said gas passage means having openings in the walls thereof forming acoustic couplings with the interior of the inner shell, said outer and inner shells being imperforate, one of said shells being formed with a plurality of substantially parallel spaced ridges which engage with the other shell to provide within the space between said inner and outer shells a plurality of sound-attenuating passages, said ridges being of less width than the width of the passages formed thereby, said ridges forming reinforcing means for the other shell to reduce vibratory movements thereof, the space between the shells being isolated from the interior of said inner shell whereby sounds entrained in the exhaust gas stream impinging upon said inner shell are damped.

7. A muflier for use with the exhaust system of an internal combustion engine, comprising a tubular sheet metal inner shell, a tubular sheet metal outer shell, and front and rear closure heads, said outer shell surrounding said inner shell and being of approximately the same length as said inner shell, said shell walls at their end zones being in contiguous relation, said closure heads having flange portions embracing the end zones of the Walls for securing the walls in fixed relation, gas inlet and outlet passages formed in said heads respectively, tubular gas passage means disposed in said inner shell, said gas passage means having openings in the walls thereof forming acoustic couplings with the interior of the inner shell, said outer and inner shells being imperforate, one of said shells being formed with a plurality of substantially parallel spaced ridges which engage with the other shell to provide within the space between said inner and outer shells a plurality of sound-attenuating passages, said ridges being in depth less than the width of said 10 passages, the space between the shells being isolated from the interior of said inner shell whereby sounds entrained in the exhaust gas stream impinging upon said inner shell are damped.

8. A mufiier for use with the exhaust system of an internal combustion engine, comprising a tubular inner shell, a tubular outer shell, and front and rear closure heads, said outer shell surrounding said inner shell and being of approximatey the same length as said inner shell, gas inlet and outlet passages formed in said heads respectively, tubular gas passage means disposed in said inner shell, said gas passage means having openings in the walls thereof forming acousti-c couplings with the interior of the inner shell, said outer and inner shells being imperforate, one of said shells being formed with a plurality of longitudinally-spaced, parallel, circumferentially-extending ridges which engage with the other shell to form between said shells a plurality of separate, circumferentially-extending air chambers which are isolated from one another and from the interior of the inner shell, whereby sounds entrained in the exhaust gas stream and impinging upon said inner shell are damped.

FLOYD E. DEREMER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 674,210 Loomls May 14, 1901 995,265 Loper June 13, 1911 1,186,572 Guibel't June 14, 1915 1,382,495 Fowles June 21, 1921 1,402,896 Schneebell Jan. 10, 1922 1,542,829 Oldberg June 23, 1925 1,608,245 Schwager Nov. 23, 1926 1,927,255 Brown Sept. 19, 1933 2,133,349 Gray Oct. 18, 1938 2,151,084 Deremer Mar. 21, 1939 2,316,437 Kercher Apr. 13, 1943 2,392,989 Kliewer Jan. 15, 1946 2,541,373 McLeod Feb. 13, 1951 2,565,184 Parlasca Aug. 21, 1951 2,618,354 I-Iedrick Nov. 18, 1952 FOREIGN PATENTS Number Country Date 435,423 Great Britain Sept. 20, 1935 

